Any non-recurring or single payment made in addition to the regular salary is a one-time payment. The pay frequency can be weekly, semimonthly, monthly or annually.
Since it could be paid along with the salary, the payroll team has to take care to get the calculation right while running the monthly payroll. Any delay or error in the payout could demoralise employees. Remember, this payment is usually linked to performance.
Employers make several one-time payments to their employees. These are a few common ones.